I IO 
T. G. B. Osborn. 
Climate and Topography. 
The city of Adelaide, the capital of South Australia, is situated 
near the eastern shores of St. Vincent’s Gulf, lat. 34° 56' S., long. 
138° 35' E. It stands on an alluvial plain about six miles from the 
coast at a height of 140 feet above sea level. To the east of the 
city the Mount Lofty ranges rise by a series of foothills to an 
altitude of 1900 feet at Mount Lofty eleven miles distant. 
The rainfall map of Australia shews that Adelaide stands in 
the area of winter rainfall, 70% of its total annual precipitation, 
which averages twenty-one inches, falling between May and October 
inclusive. Not only are the remainder of the months of the year 
deficient in rainfall but the temperatures may range very high, 
100°F. in the shade being by no means uncommon in December* 
January or February, while 118°F. has been recorded. 1 The high 
temperatures are bearable, however, on account of the dryness of 
the air. The average mean humidity is only 56, while the mean 
for the two months December and January is as low as 33. Much 
of the hot season is passed in days of cloudless sunshine. The 
prevalent wind during the summer months is south-west. This 
comes moisture-laden from the cool Southern Ocean, but being 
heated over the land it becomes a drying rather than a rain-bringing 
wind. Following a well-known cycle the winds periodically shift to 
the north, becoming intensely hot and dry, and bringing clouds of 
dust. Under these conditions evaporation rapidly rises but 
transpiration is not proportionately increased. 2 The total mean 
yearly evaporation for Adelaide is 54 inches. 
The climatic conditions prevailing in the hills are naturally 
less extreme, the temperature at Mount Lofty averaging 10 n F. 
cooler than on the plains, while the rainfall is 47 inches. The bulk 
of the rainfall is in the winter, and the summer months are 
comparatively hot and dry. 
While the climatic conditions favour the production of a flora 
adapted to xerophytic conditions the geology and topography of the 
Adelaide district are such that several different formations are to 
be met with in a comparatively restricted area. The Mount Lofty 
ranges form the western edge of the South Australian highlands 
which run in the main north and south. They form one side of the 
Great Rift Valley of Australia and the same palaeozoic strata 
1 These and other meteorological details are taken from “ The Climate 
and Meteorology of Australia,” by H. A. Hunt. Bulletin No. 1 of the Common¬ 
wealth Bureau of Meteorology, 1911. 
2 Ewart, A. J., and Rees, B. Annals of Botany, Vol. 24, 1910, p. 85. 
